1. Field of the Invention
The present invention relates to an optical head apparatus which records (writes) and/or reproduces (reads) an information signal with respect to an optical recording medium, that is, an optical disk, and to an optical disk apparatus in which the optical head apparatus is used, and in particular, to technology of protecting these apparatuses from a dust or the like.
2. Description of the Related Art
In general, an optical disk (including a magnet-optical disk) has been conventionally proposed as an optical recording medium. Moreover, an optical pickup apparatus has been proposed as an optical head apparatus for reading and writing an information signal with respect to the optical disk.
In an optical disk apparatus which is provided with the aforesaid optical pickup apparatus, the optical disk is supported by a turn table at the central portion thereof, and is rotatably driven by means of a spindle motor having a rotary shaft onto which the turn table is fixed. An objective lens of the optical pickup apparatus is located so as to oppose an information recording surface of the rotatably driven optical disk, and the optical pickup apparatus is movable in a radius direction of the optical disk along the information recording surface thereof.
The optical pickup apparatus is composed of a light source for emitting a laser light or beam, optical components such as a mirror, an objective lens and the like for converging a laser beam emitted from the light source, a photo-detector for receiving a reflected laser beam and so on. The laser beam emitted from the light source is converged by the objective lens so as to be irradiated onto the information recording surface. Then, the laser beam reflected on the information recording surface and returned transmits through the objective lens, and is received by the photo-detector, and thereby, an information signal recorded on the information recording surface is read out.
By the way, in the optical disk apparatus using the aforesaid optical pickup apparatus, a dust or the like coming into the optical disk apparatus adheres to optical components such as the objective lens or the like of the optical pickup apparatus; and for this reason, there is the possibility that optical characteristic of these optical components are deteriorated by the dust. As described above, when the dust or the like adheres to optical components such as the objective lens or the like, it is difficult to record or reproduce an information signal of the optical disk. For this reason, an error is caused in writing and reading of a required information signal; as a result, there is the possibility that the optical disk apparatus malfunctions.
In order to prevent the aforesaid malfunction, for example, the following preventive measure is considered; more specifically, the optical disk apparatus is constructed into a hermetically sealed state in a manner that dust or the like does not come into the optical disk apparatus from the outside, and thus, the dust or the like does not adhere to the optical pickup apparatus, or is hard to adhere thereto. However, it is necessary to radiate a heat of electronic components built in the optical disk apparatus, so that it is difficult to hermetically seal the optical disk apparatus. Therefore, the aforesaid measure is not a suitable countermeasure.
Moreover, there is a consideration of covering the optical components with a cover in no use of the optical pickup apparatus. An optical pickup apparatus having the cover as described above has been proposed in U.S. Pat. No. 5,995,467 and Japanese Unexamined Patent Application Publication (Kokai) No. 10-143899 filed by the applicant of this application. The above U.S. Pat. No. 5,995,467 discloses an optical disk apparatus which prevents a lens of the optical pickup apparatus from dirtying. The optical disk apparatus is provided with a shutter which is driven by means of a shutter driving means so as to be movable between a close position for hiding the objective lens and an open position for exposing the objective lens. The shutter is movable to the close position or the open position in accordance with a stop or drive operation of a mechanical chassis. Further, the above Publication (Kokai) No. 10-143899 discloses an optical pickup apparatus which prevents dust from adhering to the objective lens in no use of the optical pickup apparatus. This optical pickup apparatus has a hole through which a luminous flux emitted from the objective lens passes, and a shutter plate which is rotatably attached-to a cover for covering an actuator. When the optical pickup apparatus is moved outside a read area, the shutter plate is rotated so as to close the hole.
However, the aforesaid conventional optical disk apparatus and the optical pickup apparatus are both constructed in a manner that the shutter is rotatably attached to the cover for covering the optical pickup apparatus, and a plate thickness of the cover is thin, so that the strength thereof is relatively low. As a result, there is a problem that not only the strength of portion for supporting the shutter is low, but also there is not sufficient in a degree of freedom for constructing a mechanism of opening and closing the shutter.
The present invention has been made taking the aforesaid problem in the prior art into consideration. Therefore, an object of the present invention is to solve the above problem by providing a construction of movably attaching a shutter for opening and closing an emission surface of objective lens to a slide base on which mounted is a biaxial actuator.
To achieve the above object, the present invention provides an optical head apparatus which can securely support a shutter by movably attaching the shutter to a slide base, and can protect an objective lens from a dust by covering an emission surface of the objective lens with the shutter.
Further, to achieve the above object, the present invention provides an optical disk apparatus which comprises a spindle motor, a slide base, a biaxial actuator, a shutter and a chassis, and can securely support the shutter so as to protect an objective lens from dust or the like by covering an emission surface of the objective lens with the shutter.